Emulsion

ABSTRACT

It is an object of the present invention to provide an emulsion which shows sufficient rust preventive effect, in spite of water it contains as a constituent of the composition, on a metallic material which is otherwise corroded when coming into contact with water and oxygen.  
     The emulsion (emulsion fuel)  1  of the present invention comprises water  2  and oil (fuel oil)  3  emulsified by the aid of a surfactant  4,  characterized in that it forms a passivation film  10 P on a metallic material  10  which may be otherwise corroded when coming into contact with water and oxygen, and also forms a water-repellant layer  4 R of the surfactant molecules  4 M on the passivation film  10 p.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] This invention relates to an emulsion produced by emulsifyingwater and oil by the aid of a surfactant, more particularly such anemulsion having a sufficient rust preventive effect.

[0003] (2) Background

[0004] One of the embodiments for use of an emulsion of two types ofimmiscible liquids, e.g., water and oil, mixed by the aid of asurfactant is an emulsion fuel, which comprises water and fuel oilemulsified by the aid of a surfactant. This type of emulsion fuel hasbeen used as a fuel for diesel engines and boilers. When used for dieselengines, it is known to greatly reduce nitrogen oxide (NOx) andhydrocarbon (soot) emissions.

[0005] More concretely, it has been demonstrated that a diesel enginedischarges 30 to 40% less NOx emissions on the emulsion fuel than on thenormal fuel. Increasing proportion of water in the emulsion fuel tendsto reduce NOx emissions. For example, a 50-50 mixture almost halves theemissions from the level associated with the normal fuel.

[0006] The above-described emulsion fuel, produced by emulsifying waterand fuel oil, naturally contains a high proportion of water in thecomposition. As a result, it causes a problem of corrosion; a section ina diesel engine, boiler or the like coming directly into contact withthe emulsion fuel, more particularly a metallic section which may becorroded when coming into contact with water and oxygen, may be corrodedwhen coming into contact with water in the fuel. More concretely, a fuelinjection nozzle as a member of diesel engine is generally made of aniron-based alloy and will be corroded when coming into contact withwater in the emulsion fuel, causing problems that greatly exert adverseeffects on operating performance of the diesel engine.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide an emulsionwhich shows sufficient rust preventive effect, in spite of water itcontains as a constituent of the composition, on a metallic materialwhich is otherwise corroded when coming into contact with water andoxygen, to solve the above problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 conceptually illustrates one embodiment for producing theemulsion of the present invention,

[0009]FIG. 2 conceptually illustrates another embodiment for producingthe emulsion of the present invention,

[0010]FIG. 3 shows the relationship between redox potential of Fe (pureiron) and pH,

[0011]FIG. 4A, 4B and 4C conceptually illustrate situations of theemulsion of the present invention coming into contact with a metallicmaterial, and

[0012]FIG. 5A and 5B conceptually illustrate types of the emulsion ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0013] One of the embodiments of the emulsion of the present invention(Emulsion 1) comprises water and oil emulsified by the aid of asurfactant, which is characterized in that it forms a passivation filmon a metallic material which may be otherwise corroded when coming intocontact with water and oxygen, and also forms a water-repellant layer ofthe surfactant molecules on the passivation film.

[0014] The above constitution prevents the metallic material fromdirectly coming into contact with water and oxygen by the actions of thepassivation film and water-repellant layer formed thereon. As a result,Emulsion 1 shows sufficient rust preventive effect on a metallicmaterial which maybe otherwise corroded when coming into contact withwater and oxygen, in spite of the fact that it contains water as aconstituent of the composition.

[0015] Another embodiment of the emulsion of the present invention(Emulsion 2) is Emulsion 1, wherein the oil to be mixed with water isfuel oil as constituents of the emulsion fuel. This constitutionprevents the metallic material from directly coming into contact withwater and oxygen by the actions of the passivation film and thewater-repellant layer formed thereon. As a result, Emulsion 2 showssufficient rust preventive effect, in spite of water it contains as aconstituent of the composition, on a metallic material that maybeotherwise corroded when coming into contact with water and oxygen.Emulsion 2 with the emulsified fuel oil as a constituent shows asufficient rust preventive effect on the metallic material, and isuseable as an emulsion fuel for, e.g., diesel engines and boilers.

[0016] Still another embodiment of the emulsion of the present invention(Emulsion 3 ) is Emulsion 1 or 2, wherein the surfactant has a neutralpH and a base is incorporated to make the emulsion alkaline. Thisconstitution forms a passivation film and water-repellant layer of thesurfactant molecules thereon by the alkaline emulsion, to prevent themetallic material from directly coming into contact with water andoxygen by the actions of the passivation film and water-repellant layer.As a result, Emulsion 3 shows sufficient rust preventive effect on ametallic material which may be otherwise corroded when coming intocontact with water and oxygen, even though it contains water as aconstituent of the composition.

[0017] Still another embodiment of the emulsion of the present invention(Emulsion 4) is Emulsion 1 or 2, wherein the surfactant has an alkalinepH to make the emulsion alkaline. This constitution forms a passivationfilm and water-repellant layer of the surfactant molecules thereon bythe alkaline emulsion, to prevent the metallic material from directlycoming into contact with water and oxygen by the actions of thepassivation film and water-repellant layer. As a result, Emulsion 4shows sufficient rust preventive effect, in spite of water it containsas a constituent of the composition, on a metallic material which may beotherwise corroded when coming into contact with water and oxygen.

[0018] The present invention is described more concretely by referringto the drawings for the embodiments. FIG. 1 illustrates an embodiment ofthe emulsion of the present invention for emulsion fuel, wherein theemulsion fuel 1 (hereinafter occasionally referred to simply as the“emulsion”) is composed of water 2, a fuel oil 3, neutral surfactant(nonionic) 4 and base 5, mixed with each other to be emulsified by anemulsifier (not shown). The fuel oil 3 can be diesel fuel, heating fuel,gas turbine fuel, jet fuel, boiler fuel, etc.

[0019] Water 2, the fuel oil 3 and surfactant 4 as constituents of theemulsion fuel 1 can be mixed in a volumetric ratio of approximately100:100:1 (water:fuel oil:surfactant). The base 5 as a constituent ofthe emulsion fuel 1 is incorporated at approximately 0.5% by weightbased on the surfactant 4. The emulsion fuel 1 can be made alkaline bythe base 5. The alkalinity of the emulsion fuel 1 can vary in a pH rangeof 9 to 12 depending on types of the surfactant 4 and base 5 used.

[0020] The surfactant 4 as a constituent of the emulsion fuel 1 is notlimited so long as it helps emulsify water and oil, and various typesdescribed later (refer to FIG. 5) may be used. As an example of thenonionic surfactant, there are polyoxyethylene alkyl ethers,polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters,sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, glycerolesters, their derivatives and the like. More specifically examples ofpolyoxyethylene alkyl ethers are polyoxyethylene lauryl ether,polyoxyethylene cetyl ether, polyoxyethylene stearyl ether,polyoxyethylene oleyl ether, polyoxyethylene behenyl ether and the like;examples of polyoxyethylene alkyl phenyl ethers are polyoxyethylenenonyl phenyl ether, polyoxyethylene octyl phenyl ether and the like;examples of polyoxyethylene alkyl esters are polyethylene glycolmonolaurylate, polyethylene glycol monooleate, polyethylene glycolmonostearate and the like; examples of sorbitan alkyl esters arepolyoxyethylene sorbitan monolaurylate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan monooleate and the like; examples of polyoxyethylene sorbitanalkyl esters are polyoxyethylene sorbitan monolaurylate, polyoxyethylenesorbitan monopalmitate, polyoxyethylene sorbitan monostearate and thelike; and examples of glycerol esters are glycerol monomyristate,glycerol monostearate, glycerol monooleate and the like. Also examplesof their derivatives are polyoxyethylene alkyl amine, polyoxyethylenealkyl phenyl-formaldehyde condensate, polyoxyethylene alkyl etherphosphate and the like. Particularly preferable are nonionic surfactantsthat have an HLB value of 4 to 20.

[0021] The base 5, as a constituent of the emulsion fuel 1, can beselected from various bases, e.g., sodium or potassium compounds, solong as it is soluble in water and alkaline. One type of base or two ormore types may be used, so long as the emulsion fuel 1 is kept alkalineat pH 9 to 12.

[0022]FIG. 2 illustrates another embodiment of the emulsion of thepresent invention for emulsion fuel, wherein the emulsion fuel(emulsion) 1′ is composed of water 2′, a fuel oil 3′ and alkalinesurfactant (ionic) 4′, mixed with each other to be emulsified by anemulsifier (not shown). The emulsion fuel 1′ was made alkaline by thealkaline surfactant 4′, its alkalinity varied in a pH range of 9 to 12depending on types of the surfactant 4′ used. The surfactant 4′ as aconstituent of the emulsion fuel 1′ is not limited and may be selectedfrom various types, so long as it helps emulsify water and oil, and, atthe same time, keep the emulsion fuel 1′ at a given alkalinity (pHlevel). The surfactant can include those listed above.

[0023] The emulsion fuel 1 or 1′ was found to greatly reduce NOxemissions, almost to half of those associated with the usual fuel, whenused as the fuel for a diesel engine. No rust was observed on any memberof the diesel engine, e.g., fuel injection nozzle, in spite of use ofthe emulsion fuel 1 or 1′ for extended periods. Therefore, the emulsionfuels land 1′ show sufficient rust preventive effect, in spite of waterit contains as a constituent of the composition, on a metallic material,which is otherwise corroded when coming into contact with water andoxygen.

[0024] The mechanisms involved in the rust preventive effect of theemulsion of the present invention on a metallic material that isotherwise corroded when coming into contact with water and oxygen wereverified. It is known that rusting of iron-based alloys is controlled inan alkaline atmosphere. As shown in FIG. 3, which shows the relationshipbetween redox potential of Fe (pure iron) and pH, an iron material incontact with water is in the corrosion region when water is neutral oracidic at pH 6 (marked with a solid circle ), and in the passivationregion when water is alkaline at pH 10 (marked with an open circle 0).

[0025] An iron material is coated with a passivation film, several μm totens of μm in thickness, when its surface is exposed to an alkalineatmosphere, and the passivation film retards permeation of oxygen toprotect the material from corrosion.

[0026] A test piece of carbon steel is “rusted” when immersed in waterin a neutral to slightly acidic condition (pH: 6 to 7), whereas it isrusted but to a smaller extent, or controlled to an extent of “slightlyrusted” when immersed in water doped with a base (e.g., sodiumcarbonate) to be alkaline (pH>10), as shown by the rusting test resultswith water and water/oil emulsion (Table 1). TABLE 1 Rusting tests withwater and water/oil emulsion Neutral (pH: 6 to 7) Alkaline (pH > 10)Water Rusted Slightly rusted Emulsion Slightly rusted Not rusted(Water + Oil + Alkaline Surfactant)

[0027] It is apparent, also as shown in the rusting test results givenin Table 1, a test piece of carbon steel is not rusted when immersed inthe alkaline (pH>10) emulsion of the present invention, but the emulsiondecreases in rust preventive effect when doped with an acid (e.g.,nitric acid) to be neutral (pH: 6 to 7), so that the test piece isslightly rusted. It is apparent, therefore, that the emulsion of thepresent invention exhibits, on the premise that it contains a surfactantin the composition, sufficient rust preventive effect when keptalkaline. The sufficient rust preventive effect of the emulsion of thepresent invention comes from formation of the passivation andwater-repellant layers on a metallic material surface with which itcomes into contact, as discussed below.

[0028] As shown in FIG. 4A, 4B, the emulsion fuel 1 of the presentinvention forms, when coming into contact with a metallic material 10(e.g., fuel injection nozzle of carbon steel), a passivation film 10Pthereon as discussed earlier, because it is alkaline. The surfactant asa constituent of the emulsion fuel 1 has a hydrophilic group 4 h andhydrophobic (lipophilic) group 4 o in its molecule 4M, and is dispersedin the emulsion fuel 1, as shown in FIG. 4A, 4B. The passivation film10P, when formed on the metallic material 10, partly adsorbs thesurfactant molecules 4M on the hydrophilic group 4 h side, as shown inFIG. 4C. The passivation film 10P can also include the metallic material10 surface, which is slightly oxidized and has hydrophilicity, so thatit can adsorb the hydrophilic group 4 h in the surfactant molecule 4M.

[0029] The passivation film 10P adsorbs the hydrophilic group 4 h in thesurfactant molecule 4M more strongly than the hydrophilic groups 4 hadsorb each other. As a result, the water-repellant layer 4R of thesurfactant molecules 4M is formed on the passivation film 10P, whereineach surfactant molecule 4M is arranged, as schematically illustrated inFIG. 4C, with its hydrophobic group 4 o orienting outward (or upward inthe figure).

[0030] As described above, the emulsion fuel 1 of the present inventionforms a passivation film 10P on the metallic material 10 with which itcomes into contact, and a water-repellent layer 4R of the surfactantmolecules 4M on the film 10P. The emulsion fuel 1 of the presentinvention prevents corrosion of the metallic material 10 as far aspossible, because the passivation film 10P and water-repellent layer 4Rprevent the metallic material 10 surface from coming into contact withdissolved oxygen and water present in the emulsion fuel 1. It isneedless to say that the emulsion fuel 1′ of the present invention(comprising water, an oil and alkaline surfactant) also preventscorrosion of the metallic material 10 as far as possible in a similarmanner by forming a passivation film 10P on the metallic material 10 andwater-repellent layer 4R of the surfactant molecules on the passivationfilm 10P.

[0031] Table 2 shows results of the rusting tests with emulsion fuelsincorporated with a varying neutral surfactant. “HLB” in Table 2quantitatively indicates the hydrophilic/lipophilic balance. TABLE 2Results of the rusting tests with emulsion fuels incorporated with avarying neutral surfactant (nonionic) Rusting Rusting pH of conditionsconditions the in the in the aqueous aqueous alkaline Surfactants, (HLB)solutions solutions solutions Aromatic-based 5.73 6 +++ − ″ 10.2 6/7 ++− ″ 11.0 6/7 +++ − Branched aliphatic, nonionic 8.0 6/7 ″ 10.5 6/7 ++ −″ 12.2 6/7 +++ − Saturated, straight-chain 4 6 +++ − type nonionic ″ 8 6++ − ″ 10 6 +++ − ″ 12 6 +++ − Unsaturated, straight-chain 4 6 +++ −type nonionic ″ 7 6 +++ − ″ 11 6 +++ − ″ 12 6 +++ − Short-chain typenonionic 6 6 +++ − ″ 10 6 +++ − ″ 12 6 +++ − Long-chain type nonionic 56 +++ − ″ 10 6 +++ − ″ 20 6 ++ − Long-chain, branched 5 6 +++ − typenonionic ″ 9 6 +++ − ″ 12 6 ++ −

[0032] Rust was observed on each iron piece immersed in an aqueoussolution with approximately 1 g of the surfactant dissolved in 100 mL ofdistilled water, because the solution is neutral. On the other hand, norust was observed on each iron piece immersed in the emulsion fuel(alkaline solution) which was the above aqueous solution incorporatedwith an adequate quantity of sodium carbonate to keep the solution at pH10 to 12, irrespective of type of the surfactant used.

[0033] The surfactant as a constituent of the emulsion fuel of thepresent invention may be alkaline ionic type or neutral nonionic type.In other words, it may be used for the emulsion of the present inventionby adjusting the emulsion fuel at an alkaline pH level. The water/oilemulsion may be an O/W type with oil (oil droplets) 3 dispersed in water2 (FIG. 5A) or W/O type with water (water droplets) 2 dispersed in oil 3(FIG. 5B) The various types of surfactants shown in Table 2 includethose forming each of the above types of the emulsion, and type of theemulsion of the present invention varies depending on the type ofsurfactant used. However, it is needless to say that the emulsion of thepresent invention exhibits sufficient rust preventive effect, whether itis an O/W or W/O type.

[0034] In the above embodiments, iron-based metals (e.g., pure iron andcarbon steel) were used as the metallic materials which might becorroded on contacting water and oxygen. However, it is also needless tosay that the emulsion of the present invention exhibits sufficient rustpreventive effect on other metallic materials, e.g., copper-based andaluminum-based ones.

[0035] The above embodiments exemplify the emulsion fuels to which theemulsion of the present invention is applied. However, it is alsoneedless to say that the emulsion of the present invention iseffectively applicable to various other industrial areas, e.g., cuttingoils and coolants for various machines, and rust preventives forprotecting metallic surfaces as the special emulsion having sufficientrust preventive effect.

What we is claimed is:
 1. An emulsion comprising water and oilemulsified by the aid of a surfactant, characterized in that it forms apassivation film on a metallic material which may be otherwise corrodedwhen coming into contact with water and oxygen, and also forms awater-repellant layer of the surfactant molecules on said passivationfilm.
 2. The emulsion according to claim 1, wherein said oil to be mixedwith said water is fuel oil as constituents of an emulsion fuel.
 3. Theemulsion according to claim 1, wherein said surfactant is neutral and abase is incorporated to make said emulsion alkaline.
 4. The emulsionaccording to claim 2, wherein said surfactant is neutral and a base isincorporated to make said emulsion alkaline.
 5. The emulsion accordingto claim 1, wherein said surfactant is alkaline to make said emulsionalkaline.
 6. The emulsion according to claim 2, wherein said surfactantis alkaline to make said emulsion alkaline.